ABSTRACT This proposal is in response to AHRQ's Special Emphasis Notice on Innovative Research in Primary Care (NOT-HS-16-011). Mental disorders are pervasive and have major consequences. Primary care is the main point-of-entry for identifying and treating mental health problems in the health care system. Yet, primary care providers (PCPs) frequently struggle to effectively diagnose, treat, and manage mental health problems. The proposed research evaluates the effectiveness of a new model for supporting the delivery of mental health services in primary care ? the ?mental health eConsult.? The mental health eConsults tool allows PCPs to order a psychiatrist consultation from within a delivery system's Electronic Health Record (EHR) system. The PCP submits specific questions about a patient's care, which is routed to the organization's psychiatrists. The responding psychiatrist will have access to the patient's EHR and will deliver his/her recommendations via the EHR system within one business day, after which the PCP proceeds with care accordingly. eConsults may be a useful way to improve delivery of mental health conditions and other specialty conditions in primary care settings, but has never been rigorously evaluated for effectiveness using randomized methods. This project will analyze EHR data from a large, integrated delivery system. The research design is a cluster-randomized evaluation of the mental health eConsults tool where a randomly-selected half of the system's clinics received eConsults at baseline and the rest received eConsults 9 months later. Aim 1 is to assess the effects of receiving an eConsult on the mental health services use of patients who are seen in primary care clinics with diagnoses of mental illness. This aim will also examine whether the effects of receiving an eConsult vary by the patient's diagnosis and presence of co-located mental health services. Aim 2 is to assess the effects of receiving an eConsult on the depression symptoms of patients who are seen in primary care clinics with diagnoses of depression. By analyzing rich EHR data from a randomized study design, the proposed research will deliver robust evidence on the effectiveness of a novel approach to supporting mental health services in primary care. If shown to be effective, the eConsult model could be widely adopted in many diverse healthcare settings that have EHR systems, without major new infrastructure investments. It can be applied to pediatric and adult populations, and it could be especially useful for settings where there is limited access to specialty mental health resources, including rural populations and underserved urban populations. More broadly, this will be the first randomized evaluation of a promising Health IT-based eConsults model of supporting primary care, that could be applied to many types of specialty conditions outside of mental health.